Evaluating Trans-Benzocyclobutene-Fused Cyclooctene as a Monomer for Chemically Recyclable Polymer

Chemically recyclable polymers offer a promising solution to address the issues associated with the unsustainable use of plastics by converting the traditional linear plastic economy into a circular one. Central to developing chemically recyclable polymers is to identify the appropriate monomers that enable practical conditions for polymerization and depolymerization and ensure useful stability and material properties. Our group has recently demonstrated that trans-cyclobutane-fused cyclooctene (tCBCO) meets the abovementioned requirements and is a promising candidate for developing chemically recyclable polymers. Herein, encouraged by the success with tCBCO, we investigate the thermodynamics of polymerization of a relevant system, trans-benzocyclobutene-fused-cyclooctene, which can be viewed as tCBCO with an additional benzene ring. The study shows that introducing an additional benzene ring favors polymerization and disfavors depolymerization, and the effect is predominantly entropic. The benzo-effect can be leveraged to fine-tune the thermodynamics of polymerization and depolymerization to facilitate the chemical recycling of polymers.